1. Field of the Invention
This invention relates generally to hot top casing used in conjunction with ingot molds for the pouring of steel ingots and, more specifically to self-inverting hot top casings.
2. Brief Description of the Invention
Self-inverting hot top casings are provided with two pairs of laterally-projecting turning trunnions that are located on diametrically opposite sides of the casing. Both pairs are aligned along the vertical centerline of the hot top casing, but one pair is above and one pair is below the hot top casing's center of gravity. To lift the casing, a J-bale is engaged with a selective pair of trunnions. The J-bale is comprised of a beam having at its center an eye member to be engaged by a crane hook and having at each end a leg shaped like the letter "J". These legs are displaced from each other a suitable distance to engage a selected pair of trunnions.
Conventionally the crane lowers the J-bale to engage the pair of lower trunnions of the hot top casing after the pouring of the steel through the opening of hot top casing into the ingot mold has been completed. The crane then raises the hot top casing stripping it away from the ingot mold. As the J-bale lifts the casing from the mold, an imbalance designed into the casing creates a lateral force to cause the casing to trip, rotate about the trunnions held by the legs of the J-bale, and become inverted. The relative positions of the trunnions have now changed, and former lower trunnions have now become the upper trunnions and the formerly upper trunnions have become the lower trunnions.
The inverted casing is lowered to the floor. The casing is now relined with the thermal insert which may be comprised of panels, refractory or insulating ring, and retaining clamps as required by the particular hot top casing design being used.
When the hot top casing has been made ready for reuse, it is lifted by crane through the use of a "J" bale engaging the pair of trunnions that is now the bottom pair of trunnions. The casing self-inverts to its upright position so that it can be placed on an ingot mold for the subsequent pouring of steel and the foregoing process is repeated. When the hot top casing has been stripped from the ingot and is ready to be relined, it is again lifted by the crane and J-bale engaging the bottom set of trunnions (which were originally the upper set). The hot top casing self-inverts and is placed in the make-up area. Typical of such hot top casing is that described in U.S. Pat. No. 3,879,011.
In order for the J-bale to operate successfully, it has been necessary to displace both sets of trunnions a good distance from the casing's center of gravity. This displacement causes the casing to whip over violently when lifted, creating a great shock load on the J-bale and crane. A fast whip over can destroy ring and insert before the hot top has a chance to clear the make-up area.